The present invention relates to vacuum panel containers, and more particularly to a vacuum panel design for a hot-fill container adapted to resist the increase in container diameter (barreling) which may occur during hot filling and/or when the container is dropped on a hard surface.
A container, such as a biaxially-oriented polyethylene terephthalate (PET) beverage bottle, may be adapted to receive a hot fill product with a minimum of thermal shrinkage and distortion. Such a bottle is described in U.S. Pat. No. 4,863,046 entitled "Hot Fill Container," which issued Sept. 5, 1989 to Collette et al. The Collette et al. container is provided with a plurality of recessed vacuum panels in the middle panel section of the container, which reduce the magnitude of the vacuum generated in the filled and capped container and prevent any large uncontrolled shape distortion of the container as it contracts during product cooling. Thus, when the container is subjected to internal negative pressure as the product cools, the vacuum panels (all of them) deform and move inwardly in unison. A wrap around label covers the vacuum panels and is supported by raised wall portions in the vacuum panels, post areas between the vacuum panels, and horizontal glue lands above and below the vacuum panels. Vertical recessed ribs may be provided in the post and raised wall areas to increase the longitudinal stiffness of the panel section.
The design of the vacuum panels may vary; two other designs are illustrated in: 1) U.S. Pat. No. 315,869 entitled "Container Body For Liquids Or The Like," which issued Apr. 2, 1991 to Collette; and 2) copending and commonly-owned U.S. Ser. No. 07/792,449 entitled "Modular Mold," which was filed Nov. 15, 1991 by Collette et al., each of which is hereby incorporated by reference in its entirety.
Hot-fill containers are adapted for the packaging of liquids which must be placed in the container while hot to provide for adequate sterilization. During filling, the container is subjected to elevated temperatures on the order of 180.degree.-185.degree. F. (the product temperature) and positive internal pressures on the order of 2-5 psi (the filling line pressure). This tends to "barrel," i.e., increase the diameter of, the label panel portion of the container. Containers with excessive barreling during filling cause improper cap and label applications, and improper or inadequate vacuum panel movement (i.e., less than optimum performance under vacuum).
Also, when a filled and labeled container is dropped on a hard floor, a hydraulic hammer effect from the product causes the label panel to barrel out. Excessive barreling from even a moderate drop impact may produce a torn label, even when the container is held in a corrugated box. A bottle with excessive barreling and/or a torn label is generally unsaleable and will remain on the store shelf.
It is an object of the present invention to provide an improved vacuum panel design for a container which solves the foregoing problems of barreling. It is a further object to provide vacuum panel designs adapted for full wrap around labels or for spot labels and which also resist barreling.